title: Role of the Jun kinase pathway in the regulation of c-Jun expression and apoptosis in sympathetic neurons.
abstract: When deprived of nerve growth factor (NGF), developing sympathetic neurons die by apoptosis. This death is associated with an increase in the level of c-Jun protein and is blocked by expression of a c-Jun dominant negative mutant. Here we have investigated whether NGF withdrawal activates Jun kinases, a family of stress-activated protein kinases that can stimulate the transcriptional activity of c-Jun by phosphorylating serines 63 and 73 in the transactivation domain and which can activate c-jun gene expression. We found that sympathetic neurons contained high basal levels of Jun kinase activity that increased further after NGF deprivation. In contrast, p38 kinase, another stress-activated protein kinase that can also stimulate c-jun gene expression, was not activated after NGF withdrawal. Consistent with Jun kinase activation, we found using a phospho-c-Jun-specific antibody that c-Jun was phosphorylated on serine 63 after NGF withdrawal. Furthermore, expression of a constitutively active form of MEK kinase 1 (MEKK1), which strongly activates the Jun kinase pathway, increased c-Jun protein levels and c-Jun phosphorylation and induced apoptosis in the presence of NGF. This death could be prevented by co-expression of SEKAL, a dominant negative mutant of SAPK/ERK kinase 1 (SEK1), an activator of Jun kinase that is a target of MEKK1. In contrast, expression of SEKAL alone did not prevent c-Jun expression, increases in c-Jun phosphorylation, or cell death after NGF withdrawal. Thus, activation of Jun kinase and increases in c-Jun phosphorylation and c-Jun protein levels occur at the same time after NGF withdrawal, but c-Jun levels and phosphorylation are regulated by an SEK1-independent pathway.
authors.affiliation: Eisai London Research Laboratories, University College London, London WC1E 6BT, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Eilers
authors.forename: J
authors.initials: J
authors.lastname: Whitfield
authors.forename: C
authors.initials: C
authors.lastname: Babij
authors.forename: L L
authors.initials: LL
authors.lastname: Rubin
authors.forename: J
authors.initials: J
authors.lastname: Ham
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000502:physiology*; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D048031:JNK Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D009414:Nerve Growth Factors / Q000172:deficiency; D009474:Neurons / Q000201:enzymology / Q000378:metabolism*; D016716:PC12 Cells; D010766:Phosphorylation; D011494:Protein Kinases / Q000096:biosynthesis / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis; D016755:Proto-Oncogene Proteins c-jun / Q000096:biosynthesis* / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D017783:Superior Cervical Ganglion / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics; D048051:p38 Mitogen-Activated Protein Kinases
chemical_list: D009414:Nerve Growth Factors; D016755:Proto-Oncogene Proteins c-jun; D014157:Transcription Factors; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases